Recently, a study has been published as to why humans have sex. The study can be found here: http://www.spiegel.de/pdf/0,5534,15939,00.html (page is in German, but the pdf is English). This sounded like a perfect setting for a sparky ficathon.

Each participant received three randomly picked reasons from the list of 237 reasons to have sex that were named in the study. They could pick one, two or all three reasons to write drabbles of either 100 or 500 words or a longer story, if they desired.
Because there were so many reasons that were not used, I decided to keep the door open for future fics. All 237 reasons can be found here. Feel free to add your drabble/fic to the series.